I. Field of the Invention
The present invention relates generally to valve actuators and, more particularly, to a valve actuator utilizing a worm gear and segmented gear driving arrangement.
II. Description of the Prior Art
A plurality of valve actuators utilizing a worm gear and segmented gear driving arrangement have been previously known in the trade. These previously known valve actuators, however, suffer several disadvantages unknown to the present invention.
One disadvantage of such valve actuators is that both the worm gear and the segmented gear are exposed to the elements not only during assembly of the valve actuator onto the valve but also after the final assembly has been completed. Such exposure not only permits damage to the internal workings of the valve actuator, but also requires periodic and frequent lubrication of the valve actuator. Moreover, the accumulation of foreign debris within these valve actuators has in the past, necessitated periodic maintenance and cleaning.
Another disadvantage of these valve actuators is that no accurate and easily accessible means have been heretofore known to limit the rotational travel of the segmented gear and hence of the valve actuator shaft. Consequently, when it is desirable to actuate the valve actuator shaft only within desired predetermined rotational limits, these valve actuators have proven inadequate.
A still further disadvantage of such valve actuators is that none have included indicator means visible exteriorly of the valve actuator to indicate the rotational position of the valve actuator, and hence the degree that the valve is open or closed. As a result of this, when it has been desirable to open or close the valves a predetermined amount, the degree of valve actuation has heretofore been a matter of guesswork.